What is the basis for all the large length estimates for Spinosaurus?

[Torvosaurus]

https//:doi.org/10.26879/1110

Here are some of the points:

The sail counters an aquatic pursuit predator. It isn't retractable and is much thicker than a sailfish, for example. The sail creates drag, reducing speed and agility in the water.

Also, Spinosaurus didn't have the lateral skeletal movement to be an excellent swimmer. Regardless, the spino would have a problem capturing fish underneath it because of lack of mobility. It would also need to be a lot deeper to avoid the drag of the sail.

The spino did not have a typical cylindrical, torpedo shape of a pursuit predator. It likely couldn't tuck its legs in, like an alligator, to increase its mobility.

The density of Spinosaurus is estimated to be ~833kg/cubic meter. That's less dense than Allosaurus, but both Tyrannosaurus and Alligator were/are denser. Spinosaurus was definitely positively bouyant.

Spinosaurus isn't as short-legged as is often portrayed. Its body length/leg length is very similar to the same figures in Majungasaurus (Scott Hartman, in his blog "Road to Spinosaurus IV: not your father's JP3-osaurus"). This would have made being a terrestrial ambush predator no where near as hard as you're making it.

Spinosaurus may have been a great swimmer as far as theropods go, bit this doesn't mean it floated around waiting for food to swim up.

The feet may or may not have been webbed. I keep seeing the statement that Spinosaurus feet were webbed, but there isn't any hard evidence of that. It's based of the anatomy of the foot, but it isn't as easy as saying that it is because of anatomy.

My additional points (I don't recall if they're in the paper):

Modern waders are typical tall. But the spino is also long in the body (see my previous post). A spino wades out 10 to 20 feet and then has another 15 to 20 feet of body length out over the water, maybe more. I think that's a pretty good distance to be out into a river. In addition, its nostrils are high up on the snout, and there isn't water resistance to hold back a spinos plunge after prey.

Realistically, I think Spinosaurus is a chimera, based on too many bones from related dinosaurs to get the full skeleton correct. It may be close, but I wouldn't bet a dollar bill to a doughnut on it.

Anyways, there's a lot more in the paper, and it all points to a wader, not an aquatic predator or floater as you're proposing. Replies in papers that have been made don't counter these points, IMO.

Torvo

[andrewsaurus rex]

those are all great arguments and i've read them before.  But in my mind, it doesn't change the fact that if Spino was a wader it would have longer legs, simply because they would be advantageous and those Spinos that did happen to have slightly longer legs would get more food, breed more successfully and well, natural selection in action. 

With its shortish legs, wading out 20 feet from shore it would still have to be in relatively shallow water, or it would start floating.  Its body sticking out several feet further, well, the water still wouldn't be all that deep, unless it was good at finding underwater cliffs to stand on the edge of.  While sometimes larger fish would come into shallow water i doubt it was something a large animal could rely on for its daily bread, day after day after day.

But if it floated out into deeper water and paddle around or even float motionless, larger fish would swim by, and some would come within reach of its long arms or its long snout on the end of its long neck...no deep dives required.

I've never claimed Spino was an Olympic swimmer.  I've always recognized that sail would be a major hinderance under the water, even back when the popular theory was that Spino was a great underwater swimmer.  But its high buoyancy would make it a great floater, while it waited, patiently for its next meal, consuming very little energy floating silently.

[Cretaceous Crab]

Personally, I haven't completely ruled out the possibility of inflatable sacs on either side of the sail, similar to Prehistoric Planet's Dreadnoughtus. 

I actually sketched this concept out once, need to go find it.

[stargatedalek]

https//:doi.org/10.26879/1110

Here are some of the points:

The sail counters an aquatic pursuit predator. It isn't retractable and is much thicker than a sailfish, for example. The sail creates drag, reducing speed and agility in the water.

I think you have a strange definition of "pursuit predator". No one is saying it was a rapid swimmer like a beakfish. While the sail would have (moderately) increased drag, please explain to me how it would be any more detrimental than the large dorsal fins of orca for example, as it's a similar shape from the front. You are also taking at face value that it couldn't have served a direct role in marine hunting. If it was a slow swimming predator corralling shoals of small fish the sail could have been actively useful in doing so, like the bubble nets some baleen whales use to herd prey.

Also, Spinosaurus didn't have the lateral skeletal movement to be an excellent swimmer. Regardless, the spino would have a problem capturing fish underneath it because of lack of mobility. It would also need to be a lot deeper to avoid the drag of the sail.

Who said anything about using lateral movement to swim? It had large webbed hind feet, why would it use lateral movement? It wasn't a fish. You are creating a fake argument that no one is making to then debunk, just as frankly the authors of so many of these papers have been doing. *edit* Did you mean in reference to the tail? Because the tail is more likely to function in turning and slow movement than in a full tilt aquatic "sprint".

The spino did not have a typical cylindrical, torpedo shape of a pursuit predator. It likely couldn't tuck its legs in, like an alligator, to increase its mobility.

Again, what definition of "pursuit predator" are you using? I mentioned loons and cormorants as the closest anatomical analogues and they are if anything a wider and bulkier for their length than Spinosaurus is.

The density of Spinosaurus is estimated to be ~833kg/cubic meter. That's less dense than Allosaurus, but both Tyrannosaurus and Alligator were/are denser. Spinosaurus was definitely positively bouyant.

And again the strawman! No one has claimed it wasn't positively buoyant! I actively said that it was a surface predator and its anatomy supports this. You are trying to debunk claims that no one made to make it seem like wading is the only realistic interpretation, because you, and the papers authors, have already decided that the traditional interpretations of Spinosaurus as either a wading animal, or "dino-crocodile" is what you want to project.

Spinosaurus isn't as short-legged as is often portrayed. Its body length/leg length is very similar to the same figures in Majungasaurus (Scott Hartman, in his blog "Road to Spinosaurus IV: not your father's JP3-osaurus"). This would have made being a terrestrial ambush predator no where near as hard as you're making it.

Leg size is not relevant when it shows none of the adaptations an ambush predator of large prey has. No crushing bite, lithe frame, and frankly if anything shorter but more sturdily built legs would support the claim it hunted like a crocodile.

Spinosaurus may have been a great swimmer as far as theropods go, bit this doesn't mean it floated around waiting for food to swim up.

An animal that has adaptations for swimming at the waters surface... doesn't imply it spent it's life at the waters surface? If we really want to we could make the argument that Spinosaurus was an herbivorous grazer and was just extremely poorly adapted to such a life in every conceivable way, doesn't make that a reasonable claim. If we want to understand the most likely ways an extinct animal lived we need to look at its adaptations and follow what they actually show and imply, not fight against them because they imply something we don't like, or that varies from classical interpretations.

I also can't tell if you are trying to strawman again or you don't understand how seabirds hunt, they don't float around waiting for fish to chance to the surface, they corral them into shallow water, dive to reach fish that are within reach, follow other marine predators to trap fish between them, and use all sorts of other interesting means to actively hunt and pursue prey. I only mentioned ambush hunting while floating to emphasize that there is no reason to assume it would ambush hunt fish sitting in shallow water as opposed to doing the same behaviour while floating, and so being able to reach more fish and hunt in more variety of coastal environments.

I'm reminded of Microraptor, and the decades mainstream paleontologists spent trying to push the idea that it was a gliding animal despite various parts of its anatomy being clearly functional only for powered flight. Because it wasn't a true bird, no way it could have flown, must have just been really bad at gliding! Now their faces are covered in egg, with even so far as the molting patterns indicating Microraptor clearly flew, and I foresee the same for all of these Spinosaurus papers in due time.

The feet may or may not have been webbed. I keep seeing the statement that Spinosaurus feet were webbed, but there isn't any hard evidence of that. It's based of the anatomy of the foot, but it isn't as easy as saying that it is because of anatomy.

Enlarged, horizontally flattened toes, have only ever been seen on animals with webbed feet. This is arguing Smilodon didn't have fur.

My additional points (I don't recall if they're in the paper):

Modern waders are typical tall. But the spino is also long in the body (see my previous post). A spino wades out 10 to 20 feet and then has another 15 to 20 feet of body length out over the water, maybe more. I think that's a pretty good distance to be out into a river. In addition, its nostrils are high up on the snout, and there isn't water resistance to hold back a spinos plunge after prey.

Anyways, there's a lot more in the paper, and it all points to a wader, not an aquatic predator or floater as you're proposing. Replies in papers that have been made don't counter these points, IMO.

Torvo

On what basis are you assuming it lived near small rivers? Spinosaurus fossils are not associated with inland wetlands, let alone small rivers. They've all been found in what were believed to have been at the time coastal estuaries and lagoons. You are placing it a habitat we have no reason to assume it was in.


All of these arguments are an appeal to tradition fallacy with extra steps.

[Torvosaurus]

https//:doi.org/10.26879/1110

Here are some of the points:

The sail counters an aquatic pursuit predator. It isn't retractable and is much thicker than a sailfish, for example. The sail creates drag, reducing speed and agility in the water.

I think you have a strange definition of "pursuit predator". No one is saying it was a rapid swimmer like a beakfish. While the sail would have (moderately) increased drag, please explain to me how it would be any more detrimental than the large dorsal fins of orca for example, as it's a similar shape from the front. You are also taking at face value that it couldn't have served a direct role in marine hunting. If it was a slow swimming predator corralling shoals of small fish the sail could have been actively useful in doing so, like the bubble nets some baleen whales use to herd prey.

Also, Spinosaurus didn't have the lateral skeletal movement to be an excellent swimmer. Regardless, the spino would have a problem capturing fish underneath it because of lack of mobility. It would also need to be a lot deeper to avoid the drag of the sail.

Who said anything about using lateral movement to swim? It had large webbed hind feet, why would it use lateral movement? It wasn't a fish. You are creating a fake argument that no one is making to then debunk, just as frankly the authors of so many of these papers have been doing. *edit* Did you mean in reference to the tail? Because the tail is more likely to function in turning and slow movement than in a full tilt aquatic "sprint".

The spino did not have a typical cylindrical, torpedo shape of a pursuit predator. It likely couldn't tuck its legs in, like an alligator, to increase its mobility.

Again, what definition of "pursuit predator" are you using? I mentioned loons and cormorants as the closest anatomical analogues and they are if anything a wider and bulkier for their length than Spinosaurus is.

The density of Spinosaurus is estimated to be ~833kg/cubic meter. That's less dense than Allosaurus, but both Tyrannosaurus and Alligator were/are denser. Spinosaurus was definitely positively bouyant.

And again the strawman! No one has claimed it wasn't positively buoyant! I actively said that it was a surface predator and its anatomy supports this. You are trying to debunk claims that no one made to make it seem like wading is the only realistic interpretation, because you, and the papers authors, have already decided that the traditional interpretations of Spinosaurus as either a wading animal, or "dino-crocodile" is what you want to project.

Spinosaurus isn't as short-legged as is often portrayed. Its body length/leg length is very similar to the same figures in Majungasaurus (Scott Hartman, in his blog "Road to Spinosaurus IV: not your father's JP3-osaurus"). This would have made being a terrestrial ambush predator no where near as hard as you're making it.

Leg size is not relevant when it shows none of the adaptations an ambush predator of large prey has. No crushing bite, lithe frame, and frankly if anything shorter but more sturdily built legs would support the claim it hunted like a crocodile.

Spinosaurus may have been a great swimmer as far as theropods go, bit this doesn't mean it floated around waiting for food to swim up.

An animal that has adaptations for swimming at the waters surface... doesn't imply it spent it's life at the waters surface? If we really want to we could make the argument that Spinosaurus was an herbivorous grazer and was just extremely poorly adapted to such a life in every conceivable way, doesn't make that a reasonable claim. If we want to understand the most likely ways an extinct animal lived we need to look at its adaptations and follow what they actually show and imply, not fight against them because they imply something we don't like, or that varies from classical interpretations.

I also can't tell if you are trying to strawman again or you don't understand how seabirds hunt, they don't float around waiting for fish to chance to the surface, they corral them into shallow water, dive to reach fish that are within reach, follow other marine predators to trap fish between them, and use all sorts of other interesting means to actively hunt and pursue prey. I only mentioned ambush hunting while floating to emphasize that there is no reason to assume it would ambush hunt fish sitting in shallow water as opposed to doing the same behaviour while floating, and so being able to reach more fish and hunt in more variety of coastal environments.

I'm reminded of Microraptor, and the decades mainstream paleontologists spent trying to push the idea that it was a gliding animal despite various parts of its anatomy being clearly functional only for powered flight. Because it wasn't a true bird, no way it could have flown, must have just been really bad at gliding! Now their faces are covered in egg, with even so far as the molting patterns indicating Microraptor clearly flew, and I foresee the same for all of these Spinosaurus papers in due time.

The feet may or may not have been webbed. I keep seeing the statement that Spinosaurus feet were webbed, but there isn't any hard evidence of that. It's based of the anatomy of the foot, but it isn't as easy as saying that it is because of anatomy.

Enlarged, horizontally flattened toes, have only ever been seen on animals with webbed feet. This is arguing Smilodon didn't have fur.

My additional points (I don't recall if they're in the paper):

Modern waders are typical tall. But the spino is also long in the body (see my previous post). A spino wades out 10 to 20 feet and then has another 15 to 20 feet of body length out over the water, maybe more. I think that's a pretty good distance to be out into a river. In addition, its nostrils are high up on the snout, and there isn't water resistance to hold back a spinos plunge after prey.

Anyways, there's a lot more in the paper, and it all points to a wader, not an aquatic predator or floater as you're proposing. Replies in papers that have been made don't counter these points, IMO.

Torvo

On what basis are you assuming it lived near small rivers? Spinosaurus fossils are not associated with inland wetlands, let alone small rivers. They've all been found in what were believed to have been at the time coastal estuaries and lagoons. You are placing it a habitat we have no reason to assume it was in.


All of these arguments are an appeal to tradition fallacy with extra steps.

Did you actually read the paper? I summed up a few of the points, but the paper is where you'll find the answers. Also, a strawman argument is distorting the facts to create a platform to argue from. Hone and Holtz didn't distort or change any facts. They interpreted the facts as they are in a different way, which is what having a peer reviewed paper is about, isn't it?

Coastal estuaries and lagoons. Sounds a lot like the outer banks of the Everglades. Probably linked by small streams and coastal rivers. I'm sure the lagoons didn't just immediately drop to a 50 foot depth right where they start. And lagoons shift over time. Coastal estuaries are often shallow; take a look at the estuaries in northern Australia. You're jumping the gun by assuming what I meant.

In the paper, there is a perfectly reasonable explanation on Spinosaurus inability to dive deep, due to bouyancy and the sail. Also, whales are fully aquatic whereas Spinosaurus is not. I am truly lost on your comment about a whale's dorsal fin. Two different biological structures, with what are likely different functions, they are not the same. I am searching for a paper that says Spinosaurus swam at best 10 mph and closer to 5 most of the time. But don't quote me on that as I can't find the source. As for the lack of body flexibility, it's in the paper. All in all, there is nothing that makes  Spinosaurus a primarily aquatic predator. Occasionally maybe, but no where near competely.

So while all this floating around and corralling fish is going on, why wouldn't the spino be going after, say Onchopristis or Mawsonia? There are fossils of Spinosaurus teeth in Onchopristis, and barbs in a spinos jaw. Seriously, I can't see a 7 ton or more (I don't know what the current weight is, it has varied so much lately) dinosaur wasting time and energy to corral smaller fish when larger prey is available. Likely Onchopristis was too large to corral, and likely too fast. It doesn't make sense when comparing the energy cost to nutrition benefit for the spino to waste time on coralling fish unless it was absolutely necessary. IMO, the best way to avoid the saw is not by swimming after the sawfish, but by pulling the sawfish out of its element.

Webbed feet: There are dozens of species of aquatic birds with fully webbed feet to a fringed web around the toes. And flamingos, incidently, are waders with fully webbed feet. Seriously, the webbing on a Spinosaurus feet is not known one way or the other. I should have said that the webbing on the feet is not known and may not have been fully webbed. Your reference to Smilodon having no fur was just a bit overdone.

As for the comparison with Majungasaurus, I didn't say that Spinosaurus was a terrestrial predator. I am saying that it could catch prey on land if it needed to, and most likely by ambush. The attempt to make Spinosaurus an aquatic specialist is overlooking its ability to hunt on land if needed. It doesn't need to be taking down sauropods, but smaller dinosaurs, crocodilians, etc. were likely on its menu. Since we used Baryonyx in the recreation of its skeleton, lets say it even caught an occasional pterosaur. Seriously, I could see a spino swimming across a stretch of water and pouncing on a crocodilian similar to a jaguar pouncing on a caiman.

And isn't all of this living at the water's surface? Seriously, tell me that it isn't. Except the interpretation in the paper provides an alternative version with the spino being more terrestrial than you'd like.

Right now all anyone can do is agree that we don't know as much as we'd like and a lot is open to interpretation, which is what I'm getting at. You have your thoughts, and I have mine. It is just as likely to be wader and ambush predator as an aquatic specialist. I'm leaning towards a generalist wader. Saying I'm leaning toward "popular fallacy" with my thoughts isn't true. I find Holtz and Hone's paper more compelling than a lot of others. Just because you believe its a fallacy does not make it so.

Torvo

[BlueKrono]

Even as the conversation toes the line toward rude and accusatory, I'm just over here super impressed by the knowledge of anatomy and paleontology that some of you DTF members possess. You go, Glen Coco!

[andrewsaurus rex]

Agreed.  This forum is fortunate to have such a vast knowledge base, including the 2 members that are (lightly) sparring above.